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Patented Dec. 25, 1928.

ANDRE MOUILLEFARINE, OF PARIS, FRANCE.

DIELECTRIC SUBSTANCE AND PROCESS FOR MANUFACTURING SAME.

No Drawing. Application filed February 18, 1927, Serial No. 169,420, and in France February 18, 1924?,-

This invention has for its object to provide' a new product possessing dielectric properties equal to or higher than those of the best insulating substances as used in the industry particularly in appliances utilizing high frequency electric currents, said new product being obtained by a simple, expeditious and cheap process from suitably selected wood by treating the latter by means of one or several solutions adapted to free same from the whole of its contents of noninsulating substances and by a physico-chemical transformation of its contexture to render the whole, of its mass absolutely and invariably dielectric.

Numerous attempts have been made heretofore to manufacture particularly from wood, a material easy to obtain at low cost and in large quantities industrially, insu- 2 lating substances i. e. substances capable of withstanding without any substantial losses low or high tension electric currents .or dielectric substances i. e. substances capable of 4 similarly withstanding high frequency electric currents whereby such substances might be used to supersede the best solid dielectrics such as ebonite, vulcanite, bakelite, indiarubher, etc. Such attempts failed to give satisfactory results as the insulating substances 0 thus manufactured only had fairly bad dielectric properties which moreover dwindle down in the long run particularly when hygrometric or other ambient conditions are unfavorable.

Moreover it is a fact that the most perfect dielectric at present known being simply at-' mospheric air, attempts have been made in the course of the aforesaid experiments to create and manufacture certain .light insulating agglomerates' i. e. substances containing under a small weight a largenumber of pores that is to say of cells or small ockets full of air, the conductivity'of sai agglomerates being in an inverse ratio to the number of these air cells since their multiplicity increases, as self-explanatory, the dielectric capacity of these agglomerates. However none of such attempts has so far led to the industrial solution of the problem.

Now the present invention relates to a new product utilizable instead of ebonite, vulcanite, bakelite, indiarubber or analogous materials, either as an insulation or as a dielectric substance, said product being obtained directly from woods of suitably sewhic lected species and qualities and adapted it be dyed dark brown or black so as to 111i.-

takenly acquire the appearance of ebouit It also relates to a physico-chemical proress-inseparable from the said new prod not-whereby this dielectric substance may be manufactured industrially from these woods, said process essentially consisting, firstly, to eliminate from the numerous vessels or cells of the vascular tissue of the wood (either primary or secondary) I all their moist materials or more generally all materials making up its ligneous structure and which to various extents are conductive ,so as to merely leave a fibrous and porous i carcass constitutingby itself an insulating armature and, secondly, to fill up or stuff by capillarity the channels 'thus formed throughout the fibres of the said'tissue by means of a filling mass composed of one or w more highly insulating substances such as certain substances obtained from bituminous shales whereby the former cells of the wood previously emptied out of their conductive materials become filled up to regulatable degrees of saturation with said extraneous insulating substance or substances and thus their dielectric function is, as it were, multiplied by the insulating and supporting function of the said carcass or armature.

One feature of this process resides in the. fact that the wood having been suitably selected and cut up is first optionally submitted (in case the dielectric substance must resemble ebonite) to a dyeing bath and left therein until it has ac uired right to the heart for. instance the fine black colour of ebonite and isafterwards immersed into one or several other baths containingsubstances obtained from bituminous shales which simultaneously open out its vessels and cells and by completly eliminating therefrom the several conductive materials and fills them with an insulating mass which by capillarity or osmosepercolates through the whole mass of the wood owing to its fibres being now open and distended and thus gives same the re uired dielectric qualities.

ther features of this process and the new dielectric substance obtained therefrom will be a parent from the following description relates, by Way of example, to an industrial method of carrying it out.

According to this method and assumiiw that the dielectric substance to be Obtained me cold air.

should simulate ebonite, cut up pieces of a suitably selected Wood having fine pores such as chestnut or witch wood (the category of wood: primary wood, secondary wood,

whilst effecting this dyeing operation in the usual dyeing conditions during about 24 hours, the temperature being maintained at about 100 C. during the first 4 hours whereafter the bath is allowed to freely cool whilst the wood soaks therein duringthe remaining 20 hours. Then, after having caused the wood dyed in the aforesaid way to drip out by exposing same to the open air during about an hour or, if it is desired to hasten its drying, by exposing same to one or several hot draughts (for example in a dry kiln) the pieces or logs of wood are immersed in a liquid mass composed of one or several insulating substances obtained from bituminous shales such as ozokerite, napthtadil, hatchettin or mineral tallow previously molten by first heating the same rapidly to 150 C. which temperature corresponds to the immersion of the wood-therein, then progressively up to 300350 C. The wood is left in this hot liquid mass for approximately 3 to 4 hours so that it becomes saturated with the said insulating substances to the approximate extent of 80 to 90% whilst maintaining said mass at the aforesaid temperature of 300350 C. and afterwards withdrawn and allowed to dry naturally in It is then only suificient after having wrought it to the desired shape. (by sawing, turning or otherwise) to varnish it to give it its final finish and polished state, for instance by making use of a varnish composed of:

Shellac 35 kgs. (about 7 7 lbs.) Spirit (80 to 90) 100 kgs. (about 220 lbs.)

After being thus varnished by the usual methods and at a temperature of about 14 to 16 C., the pieces of wood either Wrought or non-wrought and entirely unrecognizable and having the true appearance of ebonite have a dielectric power which is at least equal to that of the latter substance and are thus readily utilizable for several electrical applications involving the use of ebonite.

By the operative method that has just i the species and quality of the wood treated,

said principles involving in all cases a physico-chemical treatment consisting, after optionally dyeing the wood to the heart (exclusively for giving the wood for instance the black colour that will make same ebonitelikc, it being naturally possible to do away with such dyeing step for example in cases where the dielectric substance should keep the natural tint of the wood), to eliminate from its fibres all conductive materials contained therein whilst opening them out for enabling them to be thoroughly penetrated in the same operation by fluid insulating substances in such proportions as will stuff or cram all empty cells of the opened out or )orous structure or carcass thus obtained. Vithin the scope of such directive principles and in as far as the essentiality of the abovecited operative conditions is not modified, the selection of materials, the duration, the temperature or the other operative factors may be varied without departing from the domain of the invention.

What I claim is:

The herein described process of rendering Wood dielectric, which consists first in dyeing the wood to resemble ebonite, comprising the step of immersing the wood in a liquid mass composed of basic black, acetic acid and sodium chloride for substantially twenty-four hours, the first four hours of which the mass is heated to 100 C and for the remaining time the mass is permitted to cool, thereafter submitting the wood to a heat treatment, then to the action of an insulating mass consisting of bituminous shales which first opens up the pores of the wood by removing all conductive substances therefrom and then replaces the discharged conductive substances, the action taking place during a change in temperature of the mass from 150 C. to 300 C. or more, thereafter drying the impregnated wood and finally finishing its surface with shellac bearing varnish.

In testimony whereof I afiix my signature.

ANDRE MOUILLEFARINE. 

